Cut the seitan into chunks, smaller would marinade better. For the marinade, I use about half of a tub of the vegan sourcream. To that add all the spices and the seitan (its really to taste --the beauty of Indian cooking -- so make it as spicey as you'd like). Marinade for at least half an hour, or upto overnight. Cut the onions and peppers into strips (it looks more attractive in long strips, a nice contrast to the chunky oddsized seitan). Sautee the onions in oil, and add the peppers and give it a stir for about a minute. Next add the seitan. The trick to getting the tandoori style flavour is to let the seitan char just a little bit on the outside, so sometimes, I cook the seitan separately and then add it to the veggies. To allow the flavours to blend, close the lid of the pan for about 2-3 minutes and then stir. Taste for salt. Garnish with chopped, fresh cilantro and serve hot with rice.
It is meant to be somewhat dry, and takes on a meaty-brown colour. Sometimes, to make it a little wet, I add tomatos to the onions, and once that is cooked, I blend it to a smooth paste. Then I cook the onion-tomato paste until the oil starts to float on top, and the gravy has a warm brown colour to it. Then I add the peppers and seitan and let it cook for another 6-8 minutes. While simmering the paste, add some salt, and other spices, to marry the flavours. (Just use the spices that was used in the marinade).
Please give me feedback on this recipe!